The invention utilizes a balanced, dual crank reciprocator of the type disclosed in our U.S. Pat. No. 5,674,053, issued Oct. 7, 1997, entitled, "High Pressure Compressor with Controlled Cooling During the Compression Phase," and U.S. Pat. No. 5,716,197, issued Feb. 10, 1998 entitled, "High Pressure Compressor with Internal Inter-Stage Cooled Compression having Multiple Inlets."
The present invention defines a gas compressor and dispensing station with a new and improved cyclic control system for high and ultra high pressure compressors. The compressor in this system is capable of achieving in one stage, ultra high pressure ratios of over 40/1. The invented system eliminates the need for multi-stage compressors, compressor assemblies, particularly for natural gas compressors, requiring delivery pressures of 3600-4000 psi, for NGV (natural gas vehicle) supply stations and natural gas line transportation systems.
This invention relates to a gas compressor with a new cyclic control system that is provided with a control module and sensors for controlling a group of electronically activated, electro-hydraulic valves for regulating pressurized gas flow through the compressor. The electro-hydraulic valves are selectively operated during the reciprocal cycle of the compressor in an electronic-loop of cycle control format for routing gas at two discrete pressures through separate circuits in the compressor.
In this specification, the system described in our provisional application is refined with the construction of the electro-hydraulic valves controlling flow of high pressure gases from the compressor to the respective high pressure gas receiving tanks being detailed.
The single-stage compressor of this invention is designed to be inexpensively fabricated and operated for alternate fuel vehicles. Natural gas is a relatively clean, burning fuel, and, comprised largely of methane, has advantages over other hydrocarbon fuels in minimizing production of the greenhouse gas, carbon dioxide. Although natural gas is relatively abundant, it has not been widely used as an alternate fuel for vehicles because of the lack of a distribution system. Many cities have an existing infrastructure of gas distribution lines for heating and cooking. However, these are relatively low pressure lines, 30-40 p.s.i. at the street. At this pressure, the gas volume for powering a vehicle is too large to provide the driving range deemed acceptable.
Pressurized gas vessels have been designed to contain natural gas at the high pressure necessary for the fuel capacity for the driving range desired in a reasonably sized bottle. One fueling alternative is to replace prefilled gas bottles at a refueling station. It is not economical, however to prefill bottles and deliver such prefilled bottles to fueling stations for exchange with customer bottles.
While bottles may be pre-filled on the site of the fueling station, this requires an on-site compressor, and, if a fueling station has an on-site compressor it may as well fill a customer's fuel bottle already in the customer's vehicle. For the fuel to be competitively priced compared with gasoline, the on-site compression system must be efficient and productive, requiring minimal storage of compressed gas.
The high pressure gas compressor of this invention utilizes a positive displacement compressor with an expansion gas scavenging of the residual gases in the compressor. By strategic timing of the gas flow in the compression and expansion cycle, gas can be compressed in a single stage with a resultant temperature well within the thermal limits of the structural components of the compressor.
The gas compression system of this invention is targeted toward the natural gas industry both for high pressure transportation of gas in gas lines, and for destination stations where natural gas is dispensed to customer bottles for use as a vehicle fuel. It is to be understood, however, that the gas compression system can be utilized for gasses other than fuel gas where a cost-effective, high-pressure compression is required.